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Copyright © John Lindsay, 2015

GEOG*2420

The Earth From Space


Image Resolution



John Lindsay
Fall 2015

Readings

Jensen Chapter 1 pg. 14-20

Resolution

  • Resolution is the smallest interval measurable by a scientific instrument.
  • We're referring to the resolving power of the imagining device.
  • It's related to the level of detail in the image and therefore the information content.

Types of Resolution

  • Spectral
  • Radiometric
  • Spatial
  • Temporal
  • Polarization

Spectral Resolution

  • The number and size of spectral regions the imaging device records data in
  • For example, a particular sensor may have multiple 'bands' that record within the blue, green, red, near-infrared, and thermal infrared parts of the spectrum.
Spectral resolution (source: Jensen, 2006)

Spectral Resolution

Landsat 8 bands on the spectrum
(source: USGS, 2015)
hyperspectral data cube.Airborne Visible Infrared
Imaging Spectrometer (AVIRIS)
data cube of Sullivan's Island
obtained on October 26, 1998

Radiometric Resolution

  • The sensitivity of detectors to small differences in electromagnetic energy.
Dynamic range and image bit depth
(source: Lindsay, 2013)

Spatial Resolution

  • Related to the smallest distinguishable ground feature in the image, i.e. the detail.
  • Influenced mainly by image scale.
  • Limited by the size and number of silver halide crystals in film cameras and by the number of charge-coupled device (CCD) detectors for digital cameras
  • Can be improved using a telephoto lens.
Spatial resolution (source: Jensen, 2006)
Spatial resolution (source: Jensen, 2006)

Spatial Resolution

  • A compromise exists between the spectral resolution and the spatial resolution.
  • Panchromatic bands are usually finer spatial resolution than multispectral bands.
  • This can be achieved because of the relatively coarse spectral resolution of pan images.

The Resolution Compromise

Worldview-2 stats (source: DigitalGlobe)
  • 0.46 m pan (resampled to 0.5 m); 1.8 m MS bands
  • 11-bit spectral res (2048 grey tones)

Pan-Sharpening

Pan-sharpening

Temporal Resolution

  • How often the sensor acquires data, e.g. every 30 days.
  • Temporal resolution is partly determined by orbital characteristics.
Temporal resolution (source: Unknown)
Temporal resolution

Spatial and Temporal Resolution Considerations

Temporal resolution (source: Jensen, 2006)

Polarization

  • Unpolarized energy vibrates in all possible directions perpendicular to the direction of travel.
  • Radar systems can detect polarized EMR.
Polarization resolution (source: Jensen, 2006)

Polarization

  • HH and VV configurations produce like-polarized radar imagery.
  • HV and VH configurations produce cross-polarized imagery.
Polarization effects (source: Jensen, 2006)